Conventional confocal chromatic microscope systems are installed on desktop so as to perform a vertical or lateral scan on an object for obtaining a surface profile thereof. Due to the large system volume inducing disadvantages of occupying too much space, various conventional systems are limited to perform surface profile measurement on the object, such as 8-inch wafer having a plurality of large scale integration (LSI) chips formed thereon when the volume or the surface inclined angle of the object is large, thereby reducing practicability and convenience of the entire configuration.
In the conventional arts, such as US. Pub. No. 2004/0051879, it disclosed a confocal displacement sensor wherein, through an advanced arrangement of optical outputs relative to an imaging optic in the object area of displacement sensor, real images of the optical outputs can be created at different heights. In this art, two measurement beams are created by two planar light sources, and two planar high-resolution cameras are arranged for light intensity detection. The height position of the scanned points of the surface can be calculated and the surface to be measured can be measured simultaneously at a number of scanning points. In addition, it is also known that a color sensing unit is utilized to detect the intensity ration of the object surface, whereby a surface height or depth can be obtained by calculation according to the relationship between color intensity and depth.
However, since the reflection rate with respect to RGB color of the inspection light is varied with the property of object surface, such as color of the object surface, it is necessary to establish a depth relation curve corresponding to the reflection rate of different colors for the surface profile measurement, which is inconvenient for the inspection operator. In addition, another drawback is that the slit structure is indispensable for receiving the object light from the object in the convention configuration, so that a cross talk caused by an overlap between neighboring object lights, such as unfocused lights and stray lights, will be generated inevitably, thereby decreasing effect of image detection resolution.
In addition, US2006/0012871 disclosed a confocal scanning system utilizing pinhole or slit as a confocal aperture for allowing a plurality of laser beams emitted from an illumination unit pass therethrough. The laser beams are then projected onto an object and reflected therefrom. The reflected laser beams pass through the confocal aperture and are guided to the optical detectors.
Furthermore, a “Bipolar absolute differential confocal approach to higher spatial resolution” by Zhao et al. 2004/10/18, Optical Express Vol. 12, No. 21 also disclosed a confocal inspection system for measuring the surface profile of an object, in which two pinholes are respectively arranged before and behind the corresponding collecting lens. In the system, a monochrome laser is projected onto an object through an objective and reflected therefrom for forming an object light. After that, the object light is split into two sub object lights having different optical path from each other and respectively passing through the two pinholes. The two detectors respectively detected the two sub object lights passing through the pinhole thereby obtaining the intensity signals corresponding thereto. The intensity signals are calculated through a differential algorithm for analyzing the surface profile of the object.
Moreover, Taiwan published application TW201321714 also disclosed a chromatic confocal microscope system and signal process method is provided to utilize a first optical fiber module for modulating a light into a detecting light passing through a chromatic dispersion objective and thereby forming a plurality of chromatic dispersion lights to project onto an object. A second optical fiber module conjugated with the first optical fiber module receives a reflected object light for forming a filtered light, which is split into two filtered lights detected by two color sensing units for generating two sets of RGB intensity signals, wherein one set of RGB intensity signals is biased relative to the other set of RGB intensity signals. Then two sets of RGB intensity signals are calculated for obtaining a maximum ratio factor. Finally, according to the maximum ratio factor and a depth relation curve, the surface profile of the object can be reconstructed.
In case of foregoing mentioned system having spatial filters that are arranged before and behind the focal position of the object lights, these conventional system for measuring the surface profile of the object are facing potential problems that are listed below:                (1) Defocus issue: since the object lights are detected by the optical detectors arranged before and behind the focal position, the quality of the images generated from the optical detectors will be reduced thereby increasing the inaccuracy of the inspection.        (2) Inaccuracy of image alignment: since the optical detectors are respectively arranged before and behind the focal position of the object light, the field of view (FOV) of the two optical detectors are different from each other thereby causing inspection inaccuracy.        (3) Inconsistency of spatial resolution: since the optical detectors are respectively arranged before and behind the focal position of the object light, the field of view (FOV) of the two optical detectors are different from each other thereby causing inconsistency of spatial resolution.        (4) Difficult to adjust position of optical detectors: when the chromatic dispersion objective is changed, the whole system should be calibrated especially the position of the two optical detectors, which will increase the inconveniency of the operation of the system.        